The proper diagnosis, management, and overall control of prostate cancer are major challenges in clinical oncology. Response to therapy and survival are in great part dependent on morphological and clinical parameters. If these parameters are to be of any validity, they must be applied in a standardized and reproducible fashion. Nevertheless, we know that patients with similar clinical and pathologic features may respond differently to the same therapeutic modality and have radically diverse outcomes. Recent advances in molecular biology have increased our insight into the biology of prostate cancer and the molecular events, which may be associated with aggressive behavior, resistance to therapy, and poor survival. In addition, we now have novel therapeutic modalities that target tumor-specific molecules. Thus, one of our main goals is the identification of markers associated with disease progression within states, and across states, with an aim of improving outcomes for more patients. Nevertheless, alterations of biological markers of potential clinical significance await validation studies, which in turn requires the selection of well-characterized tumor material representing different points in the natural history of the disease, and the associated clinical information. The activities of this Core support four critical functions: 1) pathologic support for the conduct of retrospective and prospective clinical studies, 2) the characterization of cohorts of patients with respect to specific markers by means of immunohistochemistry and in situ hybridization, 3) acquisition and distribution of tumor tissue to be used by our investigators through our Tumor Procurement Service, and 4) aid in the construction of c-DNAand tissue arrays.